Method for converting unsaturated organic compounds to organoboron compounds



I ;ec o l pr du t o ia k bb say lb'u'tene', ,react with aluminum-borohydride 'at v-elev organoborons -Theualkalimetal iborohydrides are now 3 mammal: eoNvE T- ORGANIC COMPOUNDS TQIORGANOBOQ I RONiCOlVlPOUNDSI.

a v e Herliert C.

fimDrawiilg, Applicationoctoberfitll flshli-. SerialNo. 619,355, r

z s Clairns." (Cl. 260 -6065! 7 This invention relates' 'to thepreparation of organo sodi m borohvdride is widely used for i 'l/ V I'Z C v the selective reduction; ofirthevcarbouyl groups in unsaturated aldehydes and ketones. No reaction has been observed in heating olefins with .,-the alkali metal.sborohydrides at; tempera tures ashighas ZOO CQ v v a The present invention is hasedupon" the discovery that V the addition of relativelyeminor-amounts,-of-aluminum chloridetiissolutionsotgsodiumi-borohydride in the dimethylether of diethyleneglycol or. the dimethylether of triethylen'eglvcol rprovidesz'a; reagent which reacts with hydrocarbons" having an olefinic double bond, such as boron compounds and more particularly to the prepara= procedure hasidisadvantageslsinceritreouiresna num;

h mallet; such as whichrhust be'reeovere T099 extended periodsbf'tirne; Thus a mixture ofl-tnisobutylborou; and .tri t butylborous.wasaobtained by the rreaction .otlisobutylene .and diborane iua sealed tube Thel reactionl is illustrated ethylene, propvlene,= 1-butene,' 2 -'but eu"e, 1'-pentene', 23 pentene-,--1 he1ieue, l-tetradeeene, diisobut'ylene, cyclw penteue, cyclohexene, styrene; aemethylstyreue, etc;, to form organoboron derivatives; The'reaction times-tare short at room temperatures but even shorterattempcrae borons of from::70:to';190E percent are easily realized.

Others solveuts maybe -utilized, such as dioxaue,,tetrahy- I,

'drofuran, diethyl-ether; tetrahydropyran and other ethers of 'monoand polyethylene glycols, in place of the dimethylether off diethylneglycol and'th'e dim'ethylether of et'riethyleneglycol. Also, other -Eriedel-Crafts catalysts may be: us'ed,: such as gallium'trichloride; and titanium tetrachloride, although ther aluminum, halides, such as aluminum chloride and aluminum .bromide, appear to w ostusefill QfilhEfCfitQlYSliS; for reasons vofrboth economy and iefiectiveness;

d vt s t ksfi e vedi d aeem e e w th-= large-excess ofnolefinic hydrocarbons.in sealed tubes-at dihoraue at 100 C for 9 6 h ours produced triethylboron.

R. SM Brokaw'and RnN.rPease (Journ; Am. Chem.

portedfth'at gaseous; olefins,- .such. asethylene, propylene vatedj. temperatures 5 to. form trialkylborons .aloug with muied alkylaluminum .hydrides, Thus, the reactionl jof ethylene with aluminum rborohydride satelr C. -isfpostulated, to, b

j Tli lastitwoi off-theabove'mentionedmethodstoifera 1 some, advantages. overthe a Grignard route in: that theyutilizeolefinsl instead Vofathe more expensive alkyl halides. However, neither diborane .nor aluminum borohydride are commercially available materials at the present time. Moreover, thecharacteristicsof these materials are such vthat v they a-re dilficulttohandle. Thus, diborane is argas,

rapidlyhydrolyzed byr-lmoisture, and :very' sensitive to air oxidation. Aluminum borohydride is also sensitive to water audmreacts-ewith(explosive violence with air..

' Thermwouldbeobvious advantagesgto the -utilization commercially available and exhibit-remarkable stability to air and water. However; .i tris-rwell -kuowu that olefinsa:

do not react with the alkali metal borohydrides. Thus,

. More---broadly-, -the1reagent used in thepractice ofithe iuventionri-may begs-defined: ajss, comprising essentially an alkali havingz-ia; valenceggr eatenithauitwo and less v than agent iu'ithe proportion of threelm-ol'esaof the borohydride tooneimole-fof,the;halide.

The; term; alkali; metal- 1borohydride i as; used 1 herein is intended tomeanithesimplealkali metal borohydrides, suchgzas :sodium borohy clride; potassium 'borohydride and,

lithium borohydride.-:; The3-term;}halide oa polyvalent metal-'3, iswgused herein to:;mean-L the chloride; iodide or bromide of true rnetalseand does not include either metalloids, such as borou or. silicon; or--- phosphorusmr sulphur.r V Theatermaunsaturated? as; used herein is intended to refer-ate: organic compouuds lwhichLowetheir vunsaturation to the-presenceof an olefinic' double-bondor an acetyleuic -triplet-l;0nd;althoughE such compoundsmay also contain an? aromatic: ring Conversely; theterm saturated as usedeherein .is? not intendedytopexclude compounds-com .taining' an aromatic ring -.havin g-asubstituted aliphatic V radical.- -.Aromatic ringsado not addbromine at room temperature whereas the other; derivativesrreact readily.

In its broadaspcet the. method of the invention is applicable for the preparation of 'oi'ganoboron corn- ;pouuds by reactingrareagent-consisting,of an alkali metal, I borohydrideeandaahalide of'aipolyvalent metal having '-fl;-;valence greater-=thantwo--and less;than-'" six jinsa liquid -carrierzwithaan unsaturatedorgauic compound; sAsgillustrative of; such :unsaturated: compounds I-:may' mention racetyleness such; aszs3-he ryne olefins suchwa s, ethylene, a V dienes such; as, butadiene,--;unsaturated acids, and" ketones and unsaturated derivatives; such; as p nitrostyre'ue, a1l-yl- 1 ethyli ctheri.and:allyldimethylamine More'ecspecially; the]: inyention gcontemplates the c011- alkylenes, to organoboron compounds haviugthe formula 1 r ra katentedsfiebsalfi l sso;

metal gboroh ydride nandgea: halide of a polyvalent v liguid.scarr i er providin'githeymetal isgriot rapidly "reduced to'zalowehvalericesby hesreage t; -fior themost rapidisa'udi complete-rreactio ,imfet h de, .flhusyxwheu sodium'borohydrldejgahd'aluminum= chloride j are used;;it:= is1:preferredr'thatgthey be; present "in the re: 1

on-metals such as cal as illustrated by the following equations: 9C H +3NaBH +AlCly3 (c 115) B+AlH +3NaCl RQB in which lire presents a'saturatedhydrocarbon radi- 3[C H5CH(CH )CH J B+3NaCI+AIH Typical results of the synthesis of trialkylborons are surnmarized in the following table where 0.2 mole olefin,

0.1 mole sodium borohydride and 0.033 mole aluminum chloride in the dimethylether of diethylene glycol as While in the practice of the present invention it is presently preferred to employ the dimethylether of diethyleneglycol or the dimethyleth'er of triethyleneglycol as the liquid carrier, other liquid carriers may befused.

Usually, however, when-the liquid carrier is not a solvent for the alkali metal borohydride, moreisatisfactory results areHobtained' if an amount of a solvent,:'such as polyethylene glycol dimethylether, suflicient to' solubilize the alkali metal borohydride-is usedinconjunction with the non-solvent liquid carrier. Thus, substantially quantitativeyields may be achieved'in certain instances with a reagent comprising sodium borohydride, .aluminum chloride and a liquid carrier containing 20 percent of the dimethylether of diethyleneglycol and 80 percent of tetrahydrofuran while only about an 85 percent yield is achieved when the liquid carrier is entirely tetrahydrofuran. a

During preliminary investigations anhydrous aluminum chloride was sublimed and dissolved in dimethylether of diethylene glycolto form a two molar solution. Sodium borohydride recrystallized from dimethylether of diethyleneglycol was dissolved in the same solvent to form a two molar solution. When equivalent amounts of sodium borohydride and aluminum chloride in this solvent are mixed,'a clear colorless solution is obtained. The absence of a precipitate indicates that thesirnple formation of aluminum borohydride is not produced as indicated by the equation:

The preparation of aluminum borohydride by reacting an alkali metal borohydride with an aluminum halide as indicated by the last equation is described in the patent to H. I. Schlesinger andH. C. Brown No. 2,599,203.

room temperature to formorganoboron compounds thus borohydride.

V i Q '4' V a .4 Y 1 indicating that the effective reactant is not aluminum The prior art previously 'mentioned indicates that a temperature of 140 C. is required for effecting the reaction of ethylene with aluminum borohydride. Also, it is known that aluminum borohydride in the presence of ethers forms ether complexes.

The trialkylborons are readily oxidized by air either in the absence of metal catalysts or, more readily, in the presence of metal catalysts, such as cobalt or mangan'ese naphthenate, or. by hydrogen .peroxide, to the corresponding boronic or borate esters. These esters are easily hydrolyzed to boric acid'and the alcohol. The reaction, therefore, provides a means of converting olefins to alcohols via the organoboron compounds. Thus, l-octene was converted to trioc'tylboron and, after oxidation and hydrolysis, an percent yield of l-octanol was realized. Similarly, l-pentene gave a percent yield of l-pentanol. Styrene yielded fi-phenylethyl alcohol and u-methylstyrene yielded fl-methyl-B-phenylethyl alcohol. \g t e The invention is illustrated further by the following examples.

Preparation of Triethylboron A two molar solution of sodium borohydride in dimethylether of diethylene glycol was placed in a copper-lined autoclave and an equal volume of a 0.7 molar solution of aluminum chloride in the same solvent was added. Ethylene was added to a pressure of 1000 pounds per square inch. The reaction mixture was heated to C. for six hours. The auto-clave was opened under nitrogen and triethylboron (B.P. 95 C.) was recovered by distillation. The yield was 60 percent.

7 Preparation of tricyclopenty lboron Into a dry 250 ml. round-bottomed flask .was placed 0.1 mole of sodium borohydride (100 ml. of 1.0 molar solution in dimethylether' of diethylene glycol);'arid 0.033 mole aluminum chloride (20ml. of a 1.66 molar solution'in the same solvent). The solutionsweremixed by, means of a'magnetic stirrer and the flask fitted with a condenser and separatory'funnel. 0.2 mole of cyclopentene were placed in the separatory funnel, the system flushed out with nitrogen, and the olefin: added. The

reaction was exothermic and the rate of addition was controlled to maintain the temperature in the desired range. At room temperature a reaction time of 3 hours wasi used. At75 C., a reaction time of 0. 5f hour w use The flask and its contents were cooled and the condenser was replaced with a vacuum distillation unit. The mixture was fractionated under reduced pressure (1 -2 mm.) to remove the solvent, followed by the organoboron compound. There was obtained 11.7 grams of borohydride in dimethylether of diethylene glycol (no added metal halide) for 48 hours.

No tricyclopentylboron was isolated. r

' 7 Preparation of tricyclohexylboron Into a 500 ml. round-bottom flask was placed 0.1 mole of lithium borohydride, 0.033 mole aluminum chloride, 0.2 mole of cyclohexene and 100ml. of diethyl' ether. The reaction mixture was heated under reflux for" 6 hours. At the end of this time, water was added and the ether layer was separated, dried and distilled. A 70 percent yield of tricyclohexylboron, B.P. 131 C. at

2 mm, was collected. All operations were 7 carried out under a n trogen atmosphere;

.andfaluminumiiodide instead g H case yields-of 50.60 periceu of het'tticyclohexylboron were realize i 1 Pe ce t y e t i y f l e yl,

7 '1367 C., and was shown to be 95 percentof l-pentanol rated compounds, such asv acetylenes, dienes and com compounds is illustratedyby the following examples.

action mixture was allowed. to warm upto' room temwas obtained 20 grams offan oilyi'liquidiwhich contained V 7 ofa'polyvalent metal having a valence from three to five .stitute'd trivinyl borane. I I a Ts a a reacted rapidly F e edt d fi fien;" aydroan chlgrideawazeyhlveg .Co gtversigtt .0 ethyl 2111216111:

my. 25:1???" Q3; .1 The reactiomwas repeated; using. aluminum thejchlorideti 5 :Eth 1 a (one our atil- Ci, water wasaddedPtodStroy residual hydride? Tlie-*organic 'layer' was" taken up in- :ether,

lnp e of ie y -c h maria Preparation of;trim pentylbbion;andpegttartb V This. reaction wasYcarried out i nera t manner as- 'realizedz V stead of cyclopentene. A yieldof 88'percetit o trilipentylboron, B.P..9495. C. at 2 mm wasobtainedi I. cgnyerslopoiqhyl 0kg! Y In a 250 ml. round-bottom flaskfw re. pl ced grams Ethyl oleate (0,1 mole )-was-treated with0z15t molaof of the tri-n-pentylboron and 30'percent hydrogen 'perw sodium;borohydride-andf 0t0'5 'mole o 'a1uminum.chloride oxide was added in two batches o' f' ml. tollowed by inthe'dimethylethermf diethylene-glycol; Aftersaxfew -s m hyd i e- A totalof tfl mli-of hyd-rominutes at- 75 0:,'the-reaction=-mixture -was .cooledi'and, gen peroxide; was added. The reaction was hi'ghly-:xo-

thermic e y n;p ide was add daattsuch-a evolved"indicated "the .utilization of threeehydrides-e per rate-asto maintain gentlerefinxingiof-z the reactionsmix- 20 mol f oleic a idgest r- The .pr0duct;-ana oi-ly ,;--lit'1uid,

' 95' "percent yield}exhibited nq-unsaturation; lt-is 'conture. At the end of the additior 1 the contents were heated on a steam cone-form few minutes, then cooled in ce, nd extracted With diethyl ether. The ether exutilized to reduce the ester group with the residual link tracts were washed with water, dried 'and distilled. reacting with the double bond to form a boron grams of the 310h01 Product w e Obtained, pound. An attempt was made to distill the product at 0.1mm. However, even with a bath temperature of 250 C., the productfailed to distill. I

I claim:

sidered that two boron hydrogem links must havexb'e en by infrared analysis. d

While the invention is particularlydirected to the conversion of olefins, such; as l-olefins, '2-olefins' and cyclo v alkylenes to the corresponding boronv compounds, its which comprises reacting an unsaturated organic combroader application to .the conversion of other unsatupoundwith an alkali-metal borohydride and a Fridel- Crafts'catalyst selected fromthe-group consisting ofchlo- T 7 rides bromides and iodides of a polyvalent metal having pounds other. thanhydrocarbons', to corresponding boron 7 a valence from three to five in an inert ethereal liquid,

Conversion ofbutadiene f d Butadiene (0.1 mole) was dissolved ;.in' the dimethyl-l ether of diethyleneglycoh A" solutionjof' sodium borehydride (0.033 mole) 'and aluminum.chloride f(0.01lf mole) in the same solvent was added to the butadiene ethereal liquidincludes anginert'solvent forgthe borohy solution at 0. C. After several hours at 0 .C. the rearylalkenes; alkenylf ethe r's and? alkenyla'mines.

hydridel perature and allowed to stay'overnight in a' nitrogen I atmosphere. Three volumes of water were'added and valentmtal is aluminum.

the organic layer was separated from the water-solvent The method'as-claimed by claim 3 wherein the alkali 1 metal'borohydride is sodium borohydride.

layer. The oily organic layer weighed '15' grams, indicating a yield of 80 percent. The materialsreacted rapidly with bromine and with oxygeni vent is selected from the group consisting of the dimethyll1 I ethers'of diethylene-glycol and tljiethylene glycol. i f r q f 9'M. 5 fil The methodof preparing an-orga'noboron compound 0.1 mole of 3-hexynerwas treated in'the same'm'anner; v as in the last precedingexamplel After hydrolysisthere borohydride and a 'Friedel-Crafts: catalyst selected'from the group consistingof chlorides,.bromides and iodides boron and exhibited unsaturationto-wa'rd bromine. -It I was, concluded that the product .must be anunsaturated in aninertethereaI liquid; borane derivative in which a boron-hydrogen link 'of the reagent had added acrossthe triple bond forming a sub- 1 :horohydride.

i To a solution of horohydride (mama);sa ami- 1; n i i a m nu hum chloride (0.011 mole) in 100 mLJOfthedimethyl- .metal borohydrideeis sodium borohydride.

" .10.; The methodas claimed Cor zversionfofitzl lyl chloride 7 Allyl chloride (0.1 mole) was treated with the re-: agent in the samemanner asin the previous example, After hydrolysis, the product was obtained as an oily to five in arrinert ethereal liquid.

, I v washed-withwater,dried and 'distilled Theproduetwas w m t e P v e m e t hi.R Pa 11Qn- 10 "collectedat 150"Cfiatflifrtrn: A""percent yield was y p ty o texeeptg hatr pext ene;lw a s i .1

1 water added to destroy residual hydride. Tlie hydrogezt 1 1. The method of preparingan organoboron compound 35 said unsaturated organiccompound being selected from 3 the] group consisting, of ;olefins,f cycloolefins, dienesg f -alkynes -arylalkenes,l-'all-ryl alkenoates," ,haloalkenes nitro- 2'." The method as'claimed byclaimlwherein the inert A dride in an amount at least sufiicient to solubilize the bore- 3. The methodas claimed .by 'cIaim Z wherein the poly -j V I i 5. The method asclaimed by cla1m;4 wherein thesol which comprises reacting an,olefin-with-analkali metali V The method asclaimed hy cla im 6 wherein" the A: {inert etherealliquidfincludes an inerti solvent for the boro "hydride inan amountat least sui ficient-to solubili ze the 1 i I Y -8.' The methodasiclaimedlbyclaim? wherein the poly gi -f'i'9; Themeth as claimed hygclaiini 8 wherein the lay claim 9' .wherein "the i olvn t isi selected-from thej group consisting o fgt he die; methylethers -of,diethylene gly'col' and triethylene glycol. .1 11. The method of preparing.;an:.organoboron com} pound which comprises reacting a l-olefinwith an alkali f}, I fnetal borohydride and a Friede'l Crafts catalyst selectedv f g from the group consisting' of'chloridesfibromides; and l V iodides of a polyvalent metal, having a valencefrom'three 1 I 12. The method as' claimed byclaim' 11 whereih the liquid which contained both chlorinefand boronr The inertetherealliquid includes an inertsolvent fortlie borofborohydride.

hydride in an amount at least sugficientto solubilize the 13". T-h'e method as 'claimed'by .claim- 12,wherein2 the polyvalent metal isaluminum.

14. The methodas claimed by claim 13 wherein the alkali metal borohydride is sodium borohydride,

15. The method as claimed by claim 14 wherein the :solvent is selected from the group consisting of. the di- 7 methylethers of diethylene glycol and triethylene glycol.

16. The method, of preparing an organoboron cornpound-which comprises reacting a Z-olefin with an alkali metal borohydride and a Fridel-Crafts catalyst selected from the group consisting of chlorides, bromides, and' iodides of a polyvalent metal having a valence from three to five in an inert ethereal liquid.

1 a '17. The method as, claimed by claim 16 wherein the inert ethereal liquid includes an inert solvent for the boro- 20. The method as claimed by claim 19 wherein the solvent is selected fro'm the. group consisting of the di- 'methylethers bf; diethylene glycol and triethylene glycol. '21. The method-"of 'prepariiig an organoboron compound which comprises re acting a lower cycloolefin with 'an alkali metal bo'riohydr ide and a Fridel-Crafts catalyst selected from the group consisting of chlorides, bromides and iodides of a polyvalent metal having a valence from three to five in an inert ethereal liquid. 7

22. The method asclaimed by claim 21 wherein the inert ethereal liquid includes an inert solvent for the borohydride in an amount at least suflicient tosolubilize the borohydride.

23. The method as claimed by claim 22 wherein the polyva lent metal is aluminum. 7 24 Themethod as claimed by claim 23 wherein the alkali metal borohydride is sodium borohydride.

25. The method as claimed by claim 24 wherein the solvent is selected from the group consisting of the dimethylethers of diethylene glycol and triethylene glycol.

No references cited. 

1. THE METHOD OF PREPARING AN ORGANOBORON COMPOUND WHICH COMPRISES REACTING AN UNSATURATED ORGANIC COMPOUND WITH AN ALKALI METAL BOROHYDRIDE AND A FRIDELCRAFTS CATALYST SELECTED FROM THE GROUP CONSISTING OF CHLORIDES, BROMIDES AND IODIDES OF A POLYVALENT METAL HAVING A VALENCE FROM THREE TO FIVE IN AN INERT ETHEREAL LIQUID, SAID UNSATURATED ORGANIC COMPOUND BEING SELECTED FROM THE GROUP CONSISTING OF OLEFINS, CYCLOOLEFINS, DIENES, ALKYNES ARYLALKENES, ALKYL ALKENOATES, HALOALKENES, NITROARYLALKENES, ALKENYL ETHERS AND ALKENYLAMINES. 